For several years I have been observing the creeping thymes I have collected from many sources, both in Britain and in Europe and I have become convinced that the two species Thymus serpyllum and T. polytrichus subsp. britannicus are in fact all one species and not two as defined by botanists. There is far too much similarity between the species, but also too many differences within each species, i.e. there is no consistency. Thymus serpyllum of southern Europe differs from that of north west Europe and Britain, in that the leaves are much bigger and the stems much longer and some of the cultivars of T. serpyllum also exhibit these characteristics, e.g. T. serpyllum 'Lemon Curd' and T. serpyllum 'Rainbow Falls'. There is debate as to the exact nature of the type specimen described by Linnaeus and his description is very brief, with no mention of hair distribution on the stems. Although botanists state that T. serpyllum only occurs in Britain in Breckland, there are in fact other wild collected plants which have the same growth pattern as Breckland thyme and which also have hairs on four sides of the stems, e.g. T. serpyllum 'Vey', which was collected in Scotland and the more recently introduced cultivar in the Thymus Coccineus Group, T. 'Bethany'. Thymus pulegioides which is widespread throughout Europe varies from a very compact low growing plant with small leaves, to a large loose bush with long trailing stems and large leaves, but with very similar DNA in the thymes which Dr. Madan Thangavelu and I have tested. This leads me to hypothesise that there could also be a similar diversity within the creeping thyme of north west Europe. However, I have an open mind regarding the relationship of the larger leaved, so called T. serpyllum, of central and southern France. I have collected thyme in France, in the Dordogne and also in Austria and the plants all have much larger leaves than T. serpyllum from Breckland. In my researches I have found two references by Jaakko Jalas which lend support to my hypothesis. In the introduction to the Flora of Iran he writes: 'Indumentum characters, including stem hairiness (whether hairy all round, on two opposite sides or along the four angles alone), are of limited taxonomical value.' This was written after Flora Europaea (post 1980). In Veroeff. Geobot. Inst. Ruebel Zuerich 191-195 (1970), writing about T. longicaulis, he refers to confusion with T. serpyllum which he regards as being restricted to north eastern France. The only way to resolve this confusion is by carrying out the Creeping Thyme DNA Study, which my colleague Dr. Madan Thangavelu and I are about to commence and which has been funded by a grant from the John Spedan Lewis Foundation. We intend using plant material from the thymes which I have collected during my field trips to sites in Britain and in Europe. |
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